U.S. Severe Weather Forecast (Coup d'œil sur la convection)

Aujourd'hui
Demain
Day Three

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Storm Prediction Center ac 011959 


Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0259 PM CDT Wednesday Jul 01 2015 


Valid 012000z - 021200z 


..there is a slight risk of severe thunderstorms from parts of eastern Kansas and MO 
to eastern Tennessee and northern al/GA... 


..there is a marginal risk of severe thunderstorms over portions of the 
northern/Central Plains to the southern Appalachians and southeast 
states... 


..there is a marginal risk of severe thunderstorms over the northeast US... 


..There is a marginal risk of severe thunderstorms over parts of Arizona... 


... 
Clusters of severe thunderstorms are possible today over parts of 
Missouri...possibly into neighboring eastern Kansas...offering 
potential for large hail...damaging gusts and a couple tornadoes. 
Damaging gusts and isolated hail also are hazards from severe storms 
moving from middle Tennessee and northern Alabama into the southern 
Appalachians region. Isolated severe storms are possible over parts 
of New York and New England...as well as the northern and central 
Great Plains and Arizona. 


..ern KS/MO... 
Forecast remains on track for this region. 


..TN to northern Georgia... 
Given ongoing convective trends across middle and eastern Tennessee into 
northern Alabama and a moderately unstable environment farther downstream 
into northern Georgia...the slight risk and severe wind probability have 
been expanded southeastward to include much of the rest of northern Georgia. 12z 
4 km NAM agrees with this scenario for a potential severe weather 
threat to move a little farther to the southeast to include the 
Atlanta metropolitan area...with storms then weakening this evening as the 
boundary layer stabilizes. 


..northern High Plains... 
Current rap-based objective analysis suggests a corridor of MLCAPE 
500-1000 j/kg extended from north-central into eastern Montana through 
western/southern South Dakota. Models continue to suggest the risk for severe storms 
should be marginal as a compact shortwave trough moves southeastward from 
Canada across this region. 


..central New York... 
Given convective trends...a small portion of central New York has been 
removed from a marginal severe risk. 


.Peters.. 07/01/2015 


Previous discussion... /issued 1119 am CDT Wednesday Jul 01 2015/ 


..TN valley into al/GA... 
A remnant mesoscale convective system from overnight convection is tracking southeastward 
across parts of western KY/TN. The air mass downstream of the mesoscale convective system 
is very moist and should become moderately unstable this afternoon 
with MLCAPE values of around 1500 j/kg. Thunderstorms are likely to 
re-intensify along the leading edge of the mesoscale convective system...posing a threat of 
locally damaging winds as they track across Tennessee into parts of al/GA. 


... 
Despite the widespread convection that affected this area last 
night...rapid heating is occurring over parts of MO into eastern Kansas. 
A shortwave trough evident over eastern Nebraska will track 
southeastward and likely aid in convective development by middle/late 
afternoon over this region. Low level and deep layer shear will 
strengthen through the day...with supercell storm structures likely. 
Hail and damaging winds are the main threats...but considerable 
veering of low level winds and effects of remnant outflow boundary 
may result in isolated tornadoes over western MO/eastern Kansas. Storms 
are expected to congeal into another mesoscale convective system during the 
evening...tracking into Arkansas. 


..Mt into Nebraska... 
Various 12z model solutions show isolated convective cells and 
clusters along a corridor from northeast Montana into eastern Nebraska this 
evening. Due to uncertainties of areal coverage will maintain only 
marginal risk at this time...but portions of this area could be upgraded 
to slight risk later today. 


..NY/New England... 
The current forecast appears on track with only slight adjustment. 
Scattered thunderstorms are expected to develop this afternoon over 
New York beneath a cool upper trough...spreading eastward into much of New 
England by evening. The stronger cells could have gusty winds and 
some hail. Present indications are that the severe threat will 
remain marginal. 


... 
Widespread thunderstorms last night have tended to stabilize the 
region somewhat. However...isolated strong to severe storms will be 
possible once again this afternoon and evening as activity forms 
over the higher terrain of eastern Arizona and propagates westward. 
Favorable effective shear profiles suggest some risk of rotating 
storms over north central Arizona...where marginal hail probabilities 
have been added. 

Mesoscale Discussion


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sels mesoscale discussion 
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Mesoscale discussion 1272 
National Weather Service Storm Prediction Center Norman OK 
0520 PM CDT Wednesday Jul 01 2015 


Areas affected...portions of far northestern MS...nrn/cntrl Alabama...nrn/cntrl 
Georgia...southeastern Tennessee...western NC...and far western SC 


Concerning...Severe Thunderstorm Watch 382... 


Valid 012220z - 012315z 


The severe weather threat for Severe Thunderstorm Watch 382 
continues. 


Summary...while an isolated strong/gusty wind threat continues in 
and near ww 382...the increasingly marginal severe risk will 
preclude the need for an additional watch...and ww 382 will be 
allowed to expire at 23z. 


Discussion...thunderstorms which moved southeastward across Tennessee and northern Alabama/Georgia 
earlier this afternoon have become increasingly displaced from 
stronger middle-level flow to their northwest. Recent radar imagery shows 
several ongoing clusters of strong convection extending along an 
instability gradient/differential heating boundary from northestern MS to 
central al/GA. While MLCAPE of 1500-2000 j/kg estimated by rap 
mesoanalysis along and S of this boundary should allow these storms 
to continue for the next several hours as they move east-southeastward with 
time...limited effective bulk shear owing to weaker middle-level winds 
with southward extent should keep storms from organizing on any more than 
a brief and isolated basis...with occasional strong/gusty winds the 
main threat. Therefore...ww 382 will be allowed to expire on 
schedule at 23z...and no additional watch appears necessary at this 
time. 


.Gleason.. 07/01/2015 


..please see www.Spc.NOAA.Gov for graphic product... 


Attention...WFO...gsp...mrx...ffc...bmx...hun...Meg... 


Latitude...Lon 33608731 34248855 34508829 34098671 34108611 34378530 
35078481 35728396 35518321 34778293 32888378 32788460 
33048579 33608731